Question

Indicate whether the following statements are true or false. If a statement is false, explain why it is false.

A. The histone proteins that constitute the core nucleosome include tetramers of histones H₂A, H₂B, H3, and H4.
B. Linker histones help compact genomic DNA by influencing the path of the DNA after it has wrapped about the nucleosome core.
C. Histone proteins have a lower-than-average number of lysines and arginines in their polypeptide chains.
D. Interphase chromosomes represent a physical state of the chromatin with the highest order of packaging.

Answer 1

A is false because histones form an octamer, not tetramers; B is true, linker histones compact DNA; C is false, histones are rich in basic amino acids; D is false as chromosomes are most compact during metaphase.

Step-by-step explanation:

Indicating whether the following statements about DNA packaging and histones are true or false:

2. A. False. The statement is false because the nucleosome core is not constituted of tetramers of H₂A, H₂B, H3, and H4 histones, rather it consists of an octamer made up of two molecules each of H2A, H2B, H3, and H4 histones. The nucleosome core is formed from eight histone proteins—two copies each of four different types of histones (H2A, H2B, H3, and H4).
3. B. True. Linker histones, such as H1, interact with the entry and exit points of the DNA as it wraps around the nucleosome core and the linker DNA, contributing to the compaction of genomic DNA into higher-order structures.
4. C. False. Histone proteins are actually rich in basic amino acids like lysines and arginines, contrasting with having a lower-than-average number of these amino acids. This high proportion of basic amino acids is vital for the binding of histones to the acidic phosphate groups of DNA.
5. D. False. Interphase chromosomes are less compact than metaphase chromosomes. The metaphase chromosomes are at their highest order of packaging, approximately 700 nm in width, in preparation for cell division.

The histones and DNA interaction is crucial for the compacting of DNA into chromatin, and while nucleosome formation is a significant step, the most compact form of chromatin is observed during metaphase with the chromosomes arranged in their most condensed state.